1. Field of the Invention
The present invention relates to liquid crystal displays, and more particularly to a display structure which provides improved performance and a method for fabricating pretilt structures, spacers and dams in a single lithographic step.
2. Description of the Related Art
Liquid crystal displays (LCD) are an important component for notebook or laptop computers. Lightweight and cost effective LCDs have enabled these portable computers to be cost effective and reliable digital tools. LCDs have even penetrated the desktop market. Therefore, improvement of LCD performance is strongly desirable.
Contrary to the desire to improve performance, approaches to improve the display performance usually increase the manufacturing cost. It should be understood that the fabrication cost of an active matrix LCD (AMLCD) is approximately proportional to the number of photo lithographic steps needed. More complicated structures are often associated with performance improvements. These additional structures typically require additional photolithographic patterns and steps.
Therefore, a need exists for a structure and fabrication method which reduces photolithographic steps while improving LCD performance.
A method for forming functional structures for a liquid crystal display, in accordance with the present invention, includes the steps of providing a substrate, patterning a first color filter layer on the substrate, patterning a second color filter layer on the first color filter layer and the substrate such that the first color filter layer and the second color filter layer overlap at predetermined locations. A third color filter layer is patterned on the second color filter layer and the substrate such that an overlap region exists between the first, second and third color filter layers at the predetermined locations. The overlap region includes a thickness of the first, second and third color filter layers. A dielectric layer is patterned on the overlap region to form the functional structures.
In alternate methods, the predetermined locations may include a periphery of the display device and the step of patterning a dielectric layer on the overlap region to form the functional structures may include the step of patterning the dielectric layer to form dam structures on the overlap regions about the periphery of the display device. The predetermined locations may include areas between pixels in an array of pixels formed on the substrate of the display device, and the step of patterning a dielectric layer on the overlap region to form the functional structures may include the step of patterning the dielectric layer to form post spacers. The step of patterning a dielectric layer on the overlap region to form the functional structures may include the step of patterning pretilt structures on pixel electrodes formed on one of the first, second, and third color filter layers other than on the overlap region.
The step of patterning pretilt structures may include patterning at least one of trenches and ridges on the pixel electrodes. The step of patterning a dielectric layer on the overlap region to form the functional structures may include the step of concurrently forming dams, post spacers and pretilt structures by patterning the dielectric layer be employing a single lithographic process.
A method for forming dams, post spacers and pretilt structures in a single lithographic step for a liquid crystal display includes the steps of providing a first substrate and a second substrate. The second substrate has at least one electrode formed thereon. A first color filter layer is patterned on the first substrate. A second color filter layer is patterned on the first color filter layer and the first substrate such that the first color filter layer and the second color filter layer overlap at predetermined locations. A third color filter layer is patterned on the second color filter layer and the first substrate such that overlap regions exist between the first, second and third color filter layers at the predetermined locations. The overlap regions include a thickness of the first, second and third color filter layers. At least one electrode is formed on the first, the second and the third color filter layers of the first substrate other than on the overlap regions. A dielectric layer is formed on the overlap regions and the at least one electrode on the first substrate to concurrently form the dams, the spacer posts on the overlap regions and the pretilt structures on regions other than the overlap regions.
In other methods, the step of assembling the first substrate and the second substrate together such that the post spacers provide a gap distance between the at least one electrode on the first substrate and the at least one electrode on the second substrate is preferably included. The method may include the step of assembling the first substrate and the second substrate together such that the dams provide a seal to prevent leakage of liquid crystal material disposed between the first and second substrates. The step of patterning a dielectric layer on the overlap regions may include the step of patterning pretilt structures which include a ridge or a trench. The overlap region may include a thickness of about one half the gap distance. The dielectric layer may include a thickness of about one half the gap distance.
Another method for forming functional structures for a liquid crystal display includes the steps of providing a substrate, patterning a first color filter layer on the substrate, patterning a second color filter layer on the first color filter layer and the substrate such that the first color filter layer and the second color filter layer overlap at predetermined locations and patterning a third color filter layer on the second color filter layer and the substrate such that an overlap region exists between the first, second and third color filter layers at the predetermined locations. The overlap region includes a thickness of the first, second and third color filter layers which is equal to a cell gap distance for the liquid crystal display.
In other methods, the predetermined locations may include a periphery of the display device, and the step of forming dam structures about the periphery of the liquid crystal display from the overlap region may be included. The predetermined locations may include areas between pixels in an array of pixels formed on the substrate of the liquid crystal display, and the method may further include the step of forming post spacers from the overlap region. The method may include the step of patterning a dielectric layer to form pretilt structures on pixel electrodes formed on one of the first, second, and third color filter layers other than on the overlap region. The step of patterning a dielectric layer to form pretilt structures may include patterning at least one of trenches and ridges on the pixel electrodes.
A liquid crystal display device, in accordance with the present invention includes a first substrate having a color filter layer formed thereon,: and the color filter layer includes at least two color filter portions. Each color filter portion corresponds to a different color. A color filter stack is formed on the color filter layer, and the color filter stack includes the color filter layer and an overlapped portion of at one least other color filter portion. A dielectric material is formed on the overlapped portion to provide a gap structure between the first substrate and a second substrate to provide a gap distance for liquid crystal disposed between the first substrate and the second substrate.
In alternate embodiments, a conductive layer may be formed on the color filter layer to form at least one electrode. The dielectric material may include a pretilt structure formed on the at least one electrode. The pretilt structure may include one of a trench structure and a ridge structure. The device may further include a conductive layer formed on the second substrate to form at least one electrode. The dielectric material may include a pretilt structure formed on the at least one electrode. The pretilt structure may include one of a trench structure and a ridge structure. The gap structure may include at least one of a dam for sealing the liquid crystal in the gap and a post spacer for providing the gap distance. The at least two color filter portions may include three color filter portions and the overlapped portion of at one least other color filter portion may include an overlapped portion of the three color filter portions. The overlapped portion of the three color filters may be about one half the gap distance in thickness or the whole gap distance. The dielectric material may be about one half the gap distance in thickness.
Another liquid crystal display device, in accordance with the present invention, includes a first substrate having a color filter layer formed thereon. The color filter layer includes at least two color filter portions, and each color filter portion corresponds to a different color. A color filter stack is formed on the color filter layer, and the color filter stack includes the color filter layer and an overlapped portion of at least one other color filter portion. The overlapped portion has a thickness employed for forming at least one of a dam structure and a post spacer to provide a gap structure between the first substrate and a second substrate to provide a gap distance for liquid crystal disposed between the first substrate and the second substrate.
In alternate embodiments, the display device may include a conductive layer formed on the color filter layer to form at least one electrode. The device may further include a dielectric material patterned on the at least one electrode to form a pretilt structure. The pretilt structure may include one of a trench structure and a ridge structure.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.